1. Field of the Invention
This invention relates to new and useful improvements in batch type pipe burnout ovens and more particularly to ovens which are efficiently heated and include air pollution control and heat recovery features.
2. Description of the Prior Art
In prior art-type coating operations, metal pipes are first burned out either in a batch type or continuous type oven. Pipes are stacked on a cart and wheeled inside a hot chamber and the temperature gradually increased to 750.degree. F. Normally it takes about 4 hours for the temperature to reach 750.degree. F. In most prior art ovens, the oven chamber is about 50' long having a combustion chamber on top or on the opposite of the door, with one blower and one burner. The oven is equipped with a supply plenum on one side. The blower delivers the heated air to the supply plenum on one side. A return air plenum on the other side receives the air which has passed over the pipe and returns it to the combustion chamber. This is a very slow process and the velocity of air within the oven chamber is very slow. Also, when the temperature within the oven chamber reaches about 300.degree.-350.degree. F. the oven starts smoking as the oil and grease begins to burn. In some cases, direct fired incinerators have been used in the exhaust stack. Comprehensive heat recovery has been difficult to achieve with such equipment. After the temperature of 750.degree. F. is reached, the pipes are pulled out of the oven and cooled down. The internal surfaces of the pipes are then sand blasted and subsequently coated with plastic or resinous coatings in one or more stages. Finally, the pipes are soaked in a separate oven at 500.degree.-550.degree. F. for a period of time so that the plastic coating applied on the inside surface is cured.